In July, Gina McCarthy, 59, was confirmed as the new head of the Environmental Protection Agency. It says a lot about President Obama that he picked someone like McCarthy for this key post. She is exactly the kind of person you want on your side in a political knife fight. An EPA veteran, she has won respect from industry thugs and tree huggers alike for her no-nonsense style. McCarthy grew up amid the old mills and factories outside Boston and still carries herself like a Southie tough who could go bare-knuckle with a polar bear. Shortly after her confirmation hearing, we met in her office in Washington, D.C., to discuss her plans at the EPA, her conversations with the president, and the future of the planet.

As a kid, was it your dream to grow up to be the head of the EPA?I can't say that. I grew up in Boston in a lower-middle-class family. My father was a teacher for 40 years. My mother waitressed, worked in a couple of doughnut shops, anything she could do to bring money in. When I was a kid, she'd drag me in at 4:30 a.m. to make these honey-dipped doughnuts called honeydews. Oh my God, they were ghastly things! I also used to go to a school that overlooked the Plymouth Rubber factory. We had to shut the windows because of the smells coming from it. I was always concerned about the health impact associated with what I was smelling and what I was being exposed to.

That's not a world one thinks is particularly concerned about environmental issues.No, but I always loved being outdoors. When I was a kid, you were sort of forced outdoors. Your parents didn't let you stay in the house.

Do you have any specific memories about pollution? Growing up, we didn't take a lot of trips. Our big "adventure in the wilderness" was going to the next town over. But I can remember Boston Harbor very clearly, and the Charles River, and you didn't go in the Boston Harbor and you didn't go in the Charles River. I remember swimming at a beach near Boston Harbor and the oil that used to get on your skin, and how you'd try to clean yourself off when you got out.

That shaped your interest in getting into public health? I started in public health at the local level, in Massachusetts. At my first job, we uncovered a PCB-contamination problem that had become a serious cancer concern for a nearby neighborhood. That got me very engaged in these issues, and the more controversial something is, the more I enjoy it.

You're in a good job for that.I know. It sort of fits.

Tell me about your conversations with President Obama when he offered you this job.We talked about his first term, and we agreed that climate change was a missing piece and that his interest was in moving climate-change initiatives forward. His speech at Georgetown [on greenhouse emissions and renewable energy] in June was one that I'd been dreaming for a president to make for a very long time. It took courage and strength. I was pretty excited about it.

Many Republicans believe each EPA regulation will be an economic catastrophe. How do you deal with that?Anyone can make a statement like that. The question is, do the facts bear it out. I don't think they do. [With climate change] no matter how many facts you put on the table, some people are going to say they're inaccurate.

The EPA has been criticized by some environmentalists for turning a blind eye to the water pollution problems of fracking for natural gas.Natural gas is part of the immediate future in the U.S. You can't go from near total reliance on fossil fuels to thinking we can shut off that reliance and move directly to renewables. It just doesn't happen. But I get that people have questions about hydro­fracking and about guaranteeing that if we're going to rely on natural gas, we need to make sure it's done safely and responsibly. The EPA is working on a robust study to understand the water-quality challenges that we're facing. We're not walking away.

Do you believe taking action on climate change is a moral issue? I do. I have for many years worried about my children's future. That's why I got into this business. I came from a culture in which people thought public service was the best thing anyone could do with their life. It has never been about making money, thank God, because I've not been tremendously successful with that. I've always felt that what EPA does matters. It's part of my moral fiber.

Al Gore once told me about what he calls the "Oh, shit" moment in climate change, when you go from understanding it as something scientists are talking about to realizing it is something that is really happening. What was yours? My "Oh, shit" moment was when I was taking on greenhouse-gas initiatives, and I realized the total disconnect between working with climate change deniers and our ability to move forward on these issues in a coherent way. The thing that bothers me about climate deniers is that I'm sure they believe that if we embrace the challenge of addressing climate, it will impact the economy in a negative way. I couldn't disagree more with that.

What kind of car do you drive?I don't have a car. Before I came to D.C., I had a Prius as my state car in Connecticut [McCarthy ran the Connecticut Department of Environmental Protection from 2004 to 2009]. The guy before me had this big car with all these lights and stuff because we had the environmental police. I told them, "No, I don't want that. You gotta fit your little radio into this Prius," and I drove one the whole time I was there.

Have we already crossed a climate change threshold from which the problem can't be fixed?The last thing I want to do is pretend to be a climate scientist. But the fortunate thing – and the unfortunate thing – is that I don't know anybody who can deny that the climate is changing. Right? We are seeing extreme weather events, and we know we need to adapt. The science is very clear. So I think it's time to figure out how to act. That's what the president has said, that's my task, and that's what the EPA is going to do.